There are wide variety of circumstances in which a compressible resilient lip seal is desired. One of these applications is the connection of a fluid filter, such as for example a transmission filter, with respect to a bore or orifice in a device such as for example a vehicular transmission. In the case of a transmission filter, the filter typically has a neck extending from the filter, which typically provides either the inlet or outlet of fluid with respect to the filter casing. This neck is typically inserted into a bore or socket that is part of the transmission or a transmission component to provide fluid communication between the filter and the transmission or transmission component. For example, the neck of the filter may be put into fluid communication with a pump inlet, a valve body, or a case casting that leads to a pump inlet.
In order to provide a seal between the filter neck and the inlet bore, it has been known to provide an elastic resilient sealing ring, or “lip seal”, which surrounds the outside of the filter neck, and sealingly fits within the bore.
A transmission filter is typically installed into the transmission during original equipment manufacture of the transmission, and may eventually be replaced by a service technician. During such an installation process, the filter neck with the resilient seal already on it is typically manually inserted in the fluid inlet bore of the transmission or transmission component. Typically, the sealing ring is inserted onto the filter neck either during assembly of the filter or at some other stage prior to insertion of the filter neck into the transmission bore. It will be appreciated that during this installation phase it is desirable to retain the sealing ring at a desired location on the neck (i.e., to prevent the seal from sliding or rolling down the neck) while also permitting the sealing ring to slide into the bore while still being compressed enough to maintain a seal between the filter neck and the bore once installed.
Various methods have been employed in order to retain the seal in its proper location on the filter neck during the installation phase. For example, the seal typically has an inner diameter when relaxed that is slightly less then the outer diameter of the location at the neck where it will be placed, so that the seal is frictionally gripping the neck. Further, a shoulder is sometimes provided on the neck to meet the edge of the seal which resists movement of the seal along the neck during the insertion phase.
During the life of a transmission, however, the filter may sometimes need to be replaced. During this replacement servicing, the filter neck is typically manually withdrawn out of the inlet bore and the filter is discarded and replaced with a new filter that is inserted in much the same fashion that is described above. This filter removal step has presented several challenges with respect to the lip seal. Oftentimes, when the filter is manually removed, the lip seal tends to slide off the neck and stay within the inlet. This problem is exacerbated by the fact that the outside of a filter neck is typically very smooth, due to the fact that the filter neck is usually an injection molded part. The inlet bore, on the other hand, tends to be a more roughly machined surface. The problem of the lip seal frictionally being left behind in the inlet, after sliding off the filter neck is also driven in part by the fact that the filter neck, which is usually an injection molded plastic part, tends to shrink due to the heat cycles experienced during its life. Some efforts at alleviating this problem have involved roughing or providing ribs or other features on the outside of the filter neck in order to help engage the lip seal during removal. This solution is not always desirable, however, as it can cause extra efforts or difficulties with respect to the injection molding process for the filter casing itself. The occurrence of the lip seal sliding off the filter neck during filter removal and being left behind in the inlet bore can have some adverse consequences. For example, the servicing technician may use tools to try to pull or scrape out the seal that has been left behind which may cause some scratching, scoring, or other damage to the inside of the bore which may then lead to a loss of a positive seal in the subsequently installed filter and sealing ring. Another disadvantage to leaving behind a lip seal is that the repair technician may not realize it has been left behind and may simply insert a new filter with its own seal into the bore, causing a stack-up of sealing rings that could cause the new sealing ring not to be seated properly or the filter not to fit correctly in the transmission.
In view of the foregoing, it would be desirable to have an improved lip seal and sealing method for sealing around the outside of a neck that is inserted into a larger bore. It would be desirable if such as seal could at least to some extent enhance the retention of the seal on the neck when the seal is removed from the bore.